Carbon black process and reactor

ABSTRACT

Stoichiometric combustion conditions are provided at a location remote from reactor walls in a carbon black process and apparatus by injecting radially inwardly hot combustion gases of a complementary composition with respect to the hot combustion gases introduced tangentially into the reactor.

This application is a continuation-in-part of my copending applicationSer. No. 895,430, filed Apr. 12, 1978, now U.S. Pat. No. 4,224,284,which is in turn a continuation-in-part of application Ser. No. 498,776,filed Aug. 19, 1974, now abandoned.

This invention relates to the manufacture of carbon black.

More particularly, the invention relates to the production of carbonblack in a tubular reactor into which hydrocarbon feed (make oil) isaxially introduced, into which hot combustion gases are tangentiallyintroduced forming a vortex around said hydrocarbon feed stream and fromwhich hydrocarbon bearing smoke is withdrawn.

BACKGROUND OF THE INVENTION

It is well known in the art to make carbon black by pyrolyticaldecomposition of a hydrocarbon, e.g., an oil. In one embodiment of suchprocesses which has proven especially successful, a tubular reactor isemployed having a longitudinal axis. The hydrocarbon feed is introducedinto such a reactor along the longitudinal axis, hot combustion gasesare tangentially fed spinning around the hydrocarbon feed stream and thehydrocarbon bearing smoke is recovered at the downstream end of such areactor.

One of the problems which still is worked upon is the structure of thecarbon black. For many applications it is desirable to produce a carbonblack with high structure, i.e., a carbon black wherein a large numberof nodules are fused together to form one aggregate. Such a highstructure carbon black is readily processable, especially when suchcarbon black is employed as a filler in rubber. The high structurecarbon black in addition has a high oil absorption which is advantageousfor some purposes. Whereas the known process outlined above produces acarbon black with good structure, there still exists a demand for anincrease of the structure of the carbon black.

The Invention

It is thus one object of the invention to provide a process for theproduction of carbon black.

Another object of this invention is to provide a process for theproducing of carbon black having increased structure.

A further object of this invention is to provide a reactor for theproduction of carbon black.

Still another object of this invention is to provide a longitudinalcarbon black reactor having axial hydrocarbon feed and tangential hotcombustion gas feed for the production of high structure carbon black.

Other objects, aspects, advantages and embodiments of this inventionwill become apparent to those skilled in the art from the followingdetailed description of the invention together with the appended claimsand the drawings of which:

FIGS. 1, 3, 5 and 7 are axial cross sections through reactors inaccordance with this invention.

FIGS. 2, 4, 6 and 8 are cross sections through the reactors shown inFIGS. 1, 3, 5 and 7, respectively, said cross sections being taken alongthe lines 2-2, 4-4, 6-6 and 8-8, respectively, in said FIGURES.

FIG. 9 shows a graph of radial and tangential velocities as a functionof the distance from the upstream confining wall.

In accordance with this invention, I have now found that a highstructure carbon black can be produced by axially introducing a firststream of hydrocarbon feed into a longitudinal reactor, bycircumferentially or tangentially introducing a second stream of hotcombustion gases into the reactor so as to form a vortex of hotcombustion gases around the first stream of hydrocarbon feed and byintroducing a third stream of gas radially into the reactor.

More specifically, I have found that if said vortex of hot combustiongases is created proximate to a confining wall the interior of whichextends radially outwardly upstream of said vortex the effect of anundesired boundary layer flow along said wall on the carbon blackstructure can be avoided or at least be markedly reduced if said thirdstream of hot combustion gases is injected in essentially radial andoutward direction close to said confining wall into the reactor. Theboundary layer flow just mentioned is not a purely radially inwardlydirected flow. This boundary layer flow rather has a certain tangentialor circumferential component resulting from the spinning movement of thegases in the vortex. Therefore, in order to counteract against theboundary layer flow which has been found to be undesirable in accordancewith this invention, the radially outwardly directed flow of a gas canbe directed in the opposite sense of the boundary layer flow. That meansthat the additional stream of gas can be directed along said upstreamconfining wall with a circumferential component in addition to theradially outwardly directed component close to the confining wall, whichadditional component has the opposite sense to the circumferentialcomponent of the boundary layer flow or vortex. Since the magnitude ofthis additional circumferential component for ideal operation dependsupon the location of the introduction

In accordance with a further embodiment of this invention, there isprovided a process for the production of carbon black wherein a firststream of hydrocarbon feed is axially introduced into a longitudinal,tubular reactor along its longitudinal axis, a second stream of hotcombustion gases resulting from combustion of a stream comprising fueland free oxygen in a nonstoichiometric composition is introducedcircumferentially into a precombustion section of said reactor to form avortex around said first stream, a third stream of hot combustion gasesresulting from combustion of a stream in a nonstoichiometric compositionof fuel and oxygen is introduced essentially radially inwardly towardthe hydrocarbon feed from at least two outlets located at a radialdistance from said hydrocarbon feed stream and located at an axialdistance from said confining wall and located circumferentially aroundthe axis of the reactor at such locations that the portions of the thirdstream stabilize themselves and flow into the feed stream but notradially out of it again, said third stream is mixed with a portion ofthe gas of said second stream in said precombustion section of saidreactor such as to form a gas mixture having stoichiometric compositionof fuel and oxygen, and said gas mixture is introduced into said firststream of hydrocarbon feed.

In this second embodiment, a very high temperature is created by thestoichiometric composition of the hot combustion gas right inside of thehydrocarbon feed without contact to the walls. This is believed tocreate a high structure carbon black. The stabilization mentioned is inthe simplest and preferred case brought out by employing an even numberof diametrically opposite outlets symmetrically arranged for creating acorresponding number of identical portions of said third radiallyinwardly directed stream.

In accordance with the first variation of the first embodiment of thisinvention, there is provided a carbon black process wherein the firststream of hydrocarbon is axially fed into a longitudinal reactorcomprising a precombustion section having an upstream wall arrangedorthogonally to the axis of the reactor connected therewith acylindrical wall and connected to said cylindrical wall a downstreamwall arranged orthogonally to the axis of the reactor in an axialcommunication and alignment with said precombustion section a reactionsection formed as a venturi, wherein a second stream of hot combustiongases is tangentially fed into said precombustion section of the reactorso as to create a vortex of hot combustion gases around said firststream, wherein a third stream of hot combustion gases is fedessentially radially outwardly into the reactor close to the interior ofsaid upstream wall and wherein a fourth stream of hydrocarbon feed isintroduced into the reactor at the throat of said venturi-shapedreaction section or downstream thereof.

In accordance with a second variation of the first embodiment of thisinvention, there is provided a carbon black process wherein up to aboutone-third or less of the combustion gases are fed radially outwardlyclosely to the upstream confining wall and two-thirds or more of the hotcombustion gases are fed tangentially into the reactor and wherein thereactor either comprises a large precombustion section and a smaller,cylindrically shaped or venturi-shaped reaction section or consistsessentially of one large cylindrical chamber.

In accordance with this invention, there is further provided a carbonblack reactor for carrying out the process of this invention. A carbonblack reactor in accordance with this invention comprises a housing withtubular-shaped interior made out of heat-resistant material, firstconduit means for the axial introduction of hydrocarbon feed into saidhousing, second conduit means for the tangential introduction ofcombustion gases into said housing, third conduit means for radialintroduction of a gas into said housing, and means to withdraw thecarbon black bearing smoke from the downstream end of the reactor.

In one embodiment of the reactor in accordance with this invention, thereactor comprises an upstream confining wall arranged essentiallyorthogonally to the longitudinal axis, said first conduit means beingarranged extending axially through said wall, said upstream confiningwall being attached to a cylindrical portion of the housing, said secondconduit means being arranged tangentially extending through saidcylindrical portion of said housing close to said upstream confiningwall, said third conduit means extending axially through said confiningwall and comprising deflecting means to deflect the third stream intoradially outward direction. In order to effectively counteract theboundary layer flow described above, the preferred reactor in accordancewith this invention is equipped with said third conduit means beingarranged so as to have their orifices or outlets facing radiallyoutwardly, i.e., away from the longitudinal axis, and close to saidupstream confining wall.

The reactor in accordance with this first embodiment of the inventioncan also comprise a large precombustion chamber and a smaller reactionsection shaped internally either cylindrically or like a venturi. Thereactor can also comprise a combined large size precombustion andreaction cylinder.

In the preferred variation of the second embodiment of this inventionthe radially inwardly directed hot combustion gas stream having acomposition which can be described as nonstoichiometric butcomplementary nonstoichiometric with respect to the nonstoichiometrichot combustion gas stream tangentially introduced, is introduced intothe reactor at a location which is at a significant distance from any ofthe reactor confining walls. Specifically, the radially inwardlydirected gas stream is injected into the reactor at a locationrelatively close to the hydrocarbon feed stream axially introduced intothe reactor. Thus, this radially inwardly introduced hot combustion gasstream will first mix with the other hot combustion gases that have beentangentially introduced into the reactor forming a stoichiometric andvery hot combustion gas mixture with then will contact the hydrocarbonfeedstream. The radially inwardly introduced hot combustion gas streamtherefore will never contact a reactor wall prior to its admixture withthe other hot combustion gases and with the hydrocarbon feedstream.

Typically, the nonstoichiometric hot combustion gases are radiallyinwardly introduced into the carbon black reactor at a distance from thereactor axis in radial direction which is less than 1/2 of the diameterof the carbon black reactor at that position and at a distance axiallydownstream from the upstream confining wall of at least 1 inch anddownstream of the orifice of the reactor releasing the hydrocarbonfeedstream in axial direction into the reactor.

In a further embodiment of the reactor of this invention, the housing ofthe reactor comprises an upstream confining wall arranged essentiallyorthogonally to the longitudinal axis, the first conduit means arearranged axially extending through said upstream confining wall, theconfining wall is attached to a cylindrical portion of the housing, thesecond conduit means are arranged tangentially extending through saidcylindrical portion of the housing close to said confining wall, thethird conduit means comprise a plurality of individual tubes extendingaxially through said confining wall and being bent by 90 degrees towardthe axis of the reactor to form orifices or outlets facing radiallyinwardly and being located at a radial distance from the hydrocarbonfeed stream and at an axial distance from the upstream confining wall.This embodiment of the reactor in accordance with this invention servesto introduce a radial stream of hot combustion gases into thehydrocarbon feed stream. The third conduit means are preferablyconnected to a source of combustion gases resulting from combustion of astream comprising oxygen and fuel in a fuel-rich composition, i.e.,these source means furnish a gas mixture comprising more fuel than thequantity which can be burned by the oxygen present. Correspondingly, thesecond conduit means are connected to a source of combustion gasesresulting from combustion of a stream comprising oxygen and fuel in anoxygen-rich composition, i.e., in the gas mixture there is more oxygenpresent than stoichiometrically necessary for the combustion of thefuel. By the arrangement of the outlets just described a gas mixture isintroduced into the hydrocarbon feed stream having a stoichiometriccomposition of fuel and oxygen thus creating a very high temperature inthe hydrocarbon feed stream without contact to the reactor walls.

The invention will be more fully understood from the following detaileddescription of the drawings and the examples of preferred embodiments ofthis invention.

In FIGS. 1 to 8, carbon black reactors are shown in two sectional viewsfor each reactor. Many details have been omitted and only the essentialportions of the reactors are shown. Each of these reactors has atubular-shaped interior with a longitudinal axis 1. The interior of thereactor comprises a refractory lining 2 which can stand very hightemperatures. The lining 2 can, e.g., consist of ceramic material. Theceramic lining 2 is encased by an insulating shell 3. Usually, a metalshell (not shown) covers the entire body of the reactor. This shell canconsist of stainless steel or any other metal conventionally used.

An inlet conduit 4 for the hydrocarbon feed which may or may not have anoutlet nozzle is positioned in the upstream end wall 5. Surrounding theinlet conduit 4 a larger conduit 6 is arranged in the upstream end wall.Through this conduit 6 a small amount of air, the so-called jacket air,is passed.

Near the upstream end wall 5 two tangential inlets 7 and 8 are arranged.Through these inlets hot combustion gases can be tangentially fed viaconduits 71 and 81 into the reactor. The direction of feed is such thatthe combustion gases introduced into the reactor will make a spinningmovement around the hydrocarbon feed stream in the same sense creating avortex of hot combustion gases surrounding the hydrocarbon feed stream.

At a location downstream of the tangential inlets, quench lines 9 and 10are located. Through these lines, e.g., water or other coolant isintroduced into the reactor in order to quench the hot smoke and stopthe carbon black formation or to modify the carbon black. At thedownstream end of the reactor the carbon black bearing smoke iswithdrawn. Usually this smoke is passed through a separating unit, e.g.,a filter, wherein the carbon black is separated from the gas andrecovered.

Referring now specifically to the reactor shown in FIGS. 1 and 2, theend wall 5 constitutes the upstream confining wall 5 of a precombustionsection 11 of the reactor. This precombustion section is further definedby a cylindrical wall 12 and a downstream confining wall 13. Bothconfining walls 5 and 13 are arranged essentially orthogonally to thelongitudinal axis 1 of the reactor. The diameter of the inlets 7 and 8is about the same as the axial length of the combustion section 11 or asthe confining interior length of the cylindrical wall 12. However, thediameters of inlets 7 and 8 can be less than the axial length of section11.

In axial alignment and open communication with the precombustion section11, a reaction section 14 with smaller internal diameter than thecombustion section is provided for. In this section the feed stream andthe hot combustion gases mix and the hydrocarbon feed is furtherpyrolytically decomposed to form carbon black. This reaction section 14can be confined by a wall 15 with a cylindrical interior as shown instraight lines in FIG. 1 or the section can be confined by aventuri-shaped wall 16 as shown in dotted lines in FIG. 1. Generally, aventuri formed out of two frustoconical portions constitutes asatisfying reaction section. However, a cylindrically choked reactionsection could also be employed.

In accordance with this invention, there are provided means to introducecombustion gases close to the interior of the upstream confining wall 5of the combustion section 11 in essentially radially outward direction.In the case of the reactor shown in FIGS. 1 and 2, these means comprisean annulus 17 arranged symmetrically around the longitudinal axis 1 ofthe reactor in the upstream confining wall 5 near the central conduit 6.An annularly shaped baffle plate 18 is attached to conduit 6. Thisbaffle plate 18 reaches sufficiently beyond (radially outwardly) theoutlet of the annulus 17 so as to deflect the combustion gasesintroduced through the annulus 17 from axial into essentially radialdirection.

The combustion gases introduced through the annulus 17 moving radiallyoutwardly constitute the counterstream to the boundary layer flowobserved in this kind of reactor. It has been found that without thesemeans for the introduction of hot combustion gases radially outwardlyclose to said upstream confining wall a stream of combustion gases frominlets 7 and 8 would flow radially inwardly as a boundary layer at theupstream confining wall in a thickness of about 1/2" 1" and cause apremature mixing of said gases with the hydrocarbon feed. This isbelieved to be detrimental to the property of high structure of thecarbon black. By means of this radially outward counterflow thepremature mixing is avoided and the carbon black will have a higherstructure.

A further embodiment of a carbon black reactor in accordance with thisinvention is shown in FIGS. 3 and 4. This reactor generally serves forthe production of large carbon black particles and its longitudinal axisis generally arranged in vertical direction. A large cylindrical chamber19 is provided for both combustion and reaction. Instead of one pair oftangential inlets 7, 8 as in the reactors shown in FIGS. 1 and 2, twosuch pairs 710, 810 and 720 (not shown), 820 are provided for tangentialintroduction of hot combustion gases. The axial feed of "make oil" isthe same as for the reactor shown in FIGS. 1 and 2. Instead of theannulus 17 and baffle plate 18 in FIG. 1, the radial counterstream flowto the upstream wall is created in this reactor by eight tubes 20, alloutlets of which are arranged in the same radial distance from thelongitudinal axis and symmetrically around said longitudinal axis of thereactor. The ends of the tubes 20 extending into the reactor are bentabout 90° so that their discharge ends shown in basically radiallyoutward direction. Through four radial inlets 21 secondary air can beblown into the reactor.

Downstream of the secondary air inlets 21, the reactor 19 is connectedto a section 22 with reduced diameter. In this section quench lines 9and 10 are arranged to quench the hot carbon black bearing smoke, e.g.,by spraying water into the reactor.

Another type of reactor is shown in FIGS. 5 and 6. The reactor comprisesa wide combustion section 11 and in axial alignment and opencommunication therewith a narrower reaction section 14 having aventuri-shaped wall 16. In this reactor only a minor portion of makeoil, namely up to about 25 percent of the total make oil, is fed axiallyinto the reactor through line 4. The rest of the make oil is fed throughat least two conduits 23, the outlets or orifices of which are arrangedso as to direct the major portion of the make oil in radially inward andaxially downstream direction toward the axis of the reactor. The inletsare so arranged as to avoid radial stream of make oil exactly at thelongitudinal axis of the reactor. Preferably, an arrangement is chosenwhich is symmetrical to the longitudinal reactor axis, e.g., by usingtwo or four identical opposing pairs of conduits 23, the orifices oroutlets of which have the same distance from and direction toward thelongitudinal axis and being disposed equidistantly circumferentiallyaround the axis of the reactor. The axial location of the orifices is atthe throat of the venturi or up to two diameters of the throatdownstream thereof.

About two-thirds or more of the toal hot combustion gases are introducedtangentially into the combustion section through conduits 71 and 81. Asmaller amount of hot combustion gases, namely up to one-third of thetotal amount of hot combustion gases, is introduced radially outwardlyclose to the upstream confining wall 5 of the combustion chamber 11through eight tubes 20, the orifices or outlets of which, being locatedinside of the reactor, point radially outwardly close to said upstreamconfining walls.

A reactor with radially inward flow of hot combustion gases is shown inFIGS. 7 and 8. The structure of this reactor is basically the same as inthe case of the reactor shown in FIGS. 1 and 2. The main differenceresides in the additional radially inwardly directed combustion gasstream.

The reactor in accordance with FIGS. 7 and 8 has eight conduits 24reaching axially through the upstream end wall and turning in an arc of90° toward the axis so that they can create a radially inwardly directedstream of gas (not a radially outwardly directed stream as in theprevious examples). The orifices 240 of these conduits 24 are located ata distance both axially from the upstream end wall (not close to saidwall as in the previous examples) and at a distance rdially from thehydrocarbon feed stream created by the nozzle 4.

The conduits 24 are all connected to a source 242 of combustion gaseswhich introduces the combustion products of a mixture of air and fuelwith less air than stoichiometrically necessary for the combustion ofall the fuel via lines 24 into the reactor. The conduits 81 and 71 forthe tangential introduction of hot combustion gases are connected to asource 82 of combustion gases which introduces the combustion productsof a mixture of air and fuel with more air than stoichiometricallynecessary for the combustion fo the fuel via lines 71 and 81 into thereactor.

During the operation of the reactor the hot combustion gas stream whichis fuel rich will mix with a portion of the surrounding hot combustiongases which are oxygen rich. The forming gas mixture enters axially intothe hydrocarbon feed stream.

Control means 25 is provided to control the quantity and/or compositionof the combustion gas introduced tangentially and radially into thereactor so that a stoichiometric combustion gas-mixture is introducedinto and mixed with the hydrocarbon feed stream. This stoichiometricmixture is at a very high temperature and will rapidly pyrolyticallydecompose the make oil. On the other hand, the mixture does not comeinto contact with any wall portions so that the high temperatures of thegas mixture has no detrimental effect on the reactor walls.

FIG. 9 of the attached drawing further illustrates the boundary layerflow discovered and eliminated in accordance with this invention. Thelower portion of FIG. 9 shows the radial velocity of gases measured in areactor having a shape very similar to that of FIG. 1. Air wasintroduced tangentially through inlets 8, nitrogen as the axial "feed".The axial length of the precombustion section 11 of this reactor wasthree inches. The diameter of section 11 has 11 inches. The radialvelocity of the gas flowing into this reactor was measured as a functionof the distance from the wall 5 (FIG. 1). The radial velocity infoot/second at 1.75 inches from the center is shown as a function of thedistance from this front end wall. The measurements have been carriedout for two different cases, one with an axial feed jet and the secondcase without an axial feed jet. The two respective curves are shown inthe lower portion of this graph. This figure clearly shows a very strongradial velocity of gases within a small boundary zone which in thepresent case is less than about a quarter of an inch. The graphs alsoshow that this boundary layer flow is independent or essentiallyindependent of whether there is an axial feedstream present or not.

Corresponding to this axial boundary layer flow, the tangential velocityclose to the upstream confining wall 5 is reduced. This is shown in theupper portion of the figure again for a case with and for a case withoutaxial feed jet. The reduced tangential velocity in the boundary layerarea, i.e. between zero and 1/4" distance from the upstream wall 5 canclearly be seen.

The results indicate that it is the boundary layer flow that causes asignificant portion of the pressure drop across the reactor. Conversely,the destruction of this boundary layer flow results in the significantreduction of the pressure drop shown in the examples above. Therefore,it is an important feature of this invention that the radially outwardlydirected flow counteracting the boundary layer flow is close to theupstream confining wall. For commercial size carbon black reactors, theboundary area in whic this boundary layer flow occurs reaches up toone-half to one inch in axial direction from the upstream wall 5. Thesecommercial size carbon black reactors have a zone 11 (FIG. 1) having anaxial length of about 12 inches, a diameter of about 24-39 inches.

The following examples illustrate the operation of carbon black reactorsin accordance with this invention. For the first example the reactorbasically corresponds to the one shown in FIG. 1, however, instead ofthe annulus 17 and the baffle plate 18, eight tubes 17' for radiallyoutward introduction of hot combustion gases are provided for, similarto those shown in FIGS. 5 and 6, for instance.

EXAMPLE I

A reactor is used in this example having the following internaldimensions:

                  TABLE 1                                                         ______________________________________                                        Axial length of the precombustion chamber                                                               12 inches                                           Diameter of the precombustion chamber                                                                   37 inches                                           Diameter of the tangential orifices                                                                     12 inches                                           Radial distance of the radial orifices                                        from the longitudinal axis                                                                              4 inches                                            Diameter of the radial orifices                                                                         1.5 inches                                          ______________________________________                                    

To produce carbon black with this reactor, Gulf oil having a Bureau ofMines Correlation Index of 120 and an average boiling point of about800° F. is axially introduced into the reactor through conduit 4. Hotcombustion gases consisting of the hot combustion products produced fromburning a mixture of air and natural gas is introduced through inlets 7and 8 into the reactor. Through the radial outlets hot combustionproducts produced from burning a mixture of air and natural gas isintroduced at a jet speed of about 500 feet per second at the outlets.The resulting carbon black will have a higher structure and the pressuredrop in the reactor will be reduced as compared to the corresponding runemploying no radial counterflow. The quantities of oil and gasintroduced are shown in the following Table 2. In the following theabbreviation gph is used to indicate gallons per hour, the abbreviationof MSCFH is used to indicate 1,000 standard cubic feet per hour.

                  TABLE 2                                                         ______________________________________                                        Oil axially through upstream end wall                                                                290    gph                                             Tangential air         200    MSCFH                                           Tangential Natural gas (1000 Btu/SCF)                                                                12     MSCFH                                           Radial air             25     MSCFH                                           Radial Natural gas     3      MSCFH                                           ______________________________________                                    

It has been found that the creation of a vortex in the precombustionchamber of a reactor causes a considerable pressure drop in the carbonblack reactor. By the radially outwardly directed counterflow close tothe upstream confining wall of the precombustion section wherein thevortex surrounding the hydrocarbon feed is created, the pressure dropcan be considerably reduced. This measure in turn can reduce pumping andoperation costs. To show this pressure drop and the influence of theradially outwardly directed flow the following example is given.

EXAMPLE II

In this example a reactor model was employed the dimensions of which areshown in the following:

                  TABLE 3                                                         ______________________________________                                         Axial length of the precombustion chamber                                                              3 inches                                            Diameter of the precombustion chamber                                                                   11 inches                                           Diameter of the tangential orifices                                                                     3 inches                                            Radial distance of the radial outlets                                         from the longitudinal axis                                                                              1.5 inches                                          Diameter of the cylindrical reaction                                          section                   3 inches                                            ______________________________________                                    

This reactor was gometrically similar to the larger reactor described inExample I and corresponds basically to the reactor shown in FIG. 1 insolid lines with the exception that instead of the annulus 17 and thebaffle plate 18, eight tubes 17' with radially outwardly directedorifices have been employed to introduce the additional hot combustiongas.

Into the reactor described nitrogen has been fed axially. Through thehot combustion gas inlets air was introduced tangentially and radially.The respective quantities of the gases introduced are shown in thefollowing table. Six runs have been carried out and the runs to becompared are the runs 1 and 2, 3 and 4, 5 and 6, respectively. Theoverall quantity of air and nitrogen in these pairs of runs has beenreduced from runs 1-2 to runs 5-6. The results with respect to thepressure drop are also shown in the following table. The upstreampressure was measured upstream of the tangential inlet 7 in therespective tunnel conduit 71. The downstream pressure was measured about4 feet downstream of the combustion section. In the following table thequantities of air or nitrogen are given in scfh (standard cubic feet perhour) and the pressure difference is shown in inches of mercury.

                  TABLE 4                                                         ______________________________________                                              Air       Air      Nitrogen                                                   through   through  Feed          Pressure                               Run   Tangential                                                                              Radial   Through                                                                              Δ P =                                                                          Drop                                   No.   Inlets 28 Inlets 6 Tube 4 P.sub.1 - P.sub.2                                                                    Reduction                              ______________________________________                                        1     12,700    0        810    0.48                                          2     10,700    2,000    810    0.30   37%                                    3     10,700    0        680    0.36                                          4      8,700    2,000    680    0.15   58%                                    5      8,700    0        560    0.23                                          6      6,700    2,000    560    0.08   65%                                    ______________________________________                                    

The data of this Table 4 show that by radially outwardly introducing gasclose to the upstream confining wall of a precombustion section thepressure drop in the carbon black reactor having axial hydrocarbon feedand tangential hot combustion gas feed can be considerably reduced. Fora large reactor with a reaction section of 12 inch diameter describedabove, the known pressure drop of 2.2 psi can be reduced to 1.4 psi bysplitting a total 225 MSCFH of combustion gases into 190 MSCFHtangentially and 35 MSCFH radially fed combustion gases. This decreaseof about 35 percent of the pressure drop makes possible a higherthroughput of make oil and hot combustion gases with otherwise unchangedequipment; this results in an increase of carbon black production ofabout 20 to about 25 percent.

EXAMPLE III

In the following example the effect of the radial counterflow on aventuri-shaped reactor will be shown. This reactor is basically of thesame type as the cylindrical reactor described. The main differencebetween the two types of reactors is that the reaction section of thisreactor is venturi-shaped as shown in FIG. 1 in dotted lines. Thedimensions of the reactor are shown in the following Table 5.

                  TABLE 5                                                         ______________________________________                                        Axial length of the precombustion chamber                                                              3     inches                                         Diameter of the precombustion chamber                                                                  11    inches                                         Diameter of the tangential orifices                                                                    3     inches                                         Radial distance of the radial orifices                                        from the axis            1.5   inches                                         Diameter of the radial orifices                                                                        1/4inch                                              Upstream diameter of the venturi                                              reaction section         3     inches                                         Throat diameter of the venturi reaction                                       section                  1.4   inches                                         Downstream diameter of the venturi                                            reaction section         3     inches                                         Angle of the converging portion of                                            the venturi reaction section to the                                           longitudinal axis        15°                                           Angle of the diverging portion of the                                         venturi reaction section to the                                               longitudinal axis        8°                                            ______________________________________                                    

Into the reactor thus described air was introduced tangentially andnitrogen was introduced axially. Two runs were carried out, one withradial introduction of a portion of the air and the other with all theair being introduced tangentially. The upstream pressure P₁ was measuredin the conduit 81 close to the tangential orifice. The downstreampressure P₂ was measured about 15 reaction section diameters downstreamof the upstream end wall of the reactor. The volumes employed and thepressure drops measured are shown in the following Table 6.

                  TABLE 6                                                         ______________________________________                                        Run No.            7          8                                               Axial nitrogen (scfh)                                                                            810        810                                             Tangential air (scfh)                                                                            12,700     10,700                                          Radial air (scfh)  --         2,000                                           Pressure drop = P.sub.1 - P.sub.2 (in. Hg)                                                       1.39       0.84                                            ______________________________________                                    

The data of Table 6 show that the radial introduction of gas in thisexample lowers the pressure drop of a venturi-shaped reactor by about 40percent. Therefore, a considerably higher amount of oil per hour can beconverted into carbon black under the same conditions of initialpressure, pump sizes, reactor dimensions, etc., as compared to the samereactor operated without radial counterflow.

EXAMPLE IV

In the following example carbon black was made in a carbon black reactorhaving a venturi-shaped reaction section. The oil used for hydrocarbonfeed was Ponca oil having a Bureau of Mines Correlation Index of 124.The gas employed as the fuel for the hot combustion gases was propane.The dimensions of the reactor employed are shown in the following Table7.

                  TABLE 7                                                         ______________________________________                                        Axial length of the precombustion chamber                                                             4      inches                                         Diameter of the precombustion chamber                                                                 10     inches                                         Diameter of the tangential orifices                                                                   3      inches                                         Radius of baffle plate from the axis                                                                  0.75   inch                                           Distance of baffle plate from upstream                                        end wall                3/8    inch                                           Upstream diameter of the venturi                                              reaction section        3      inches                                         Thoat diameter of the venturi reaction                                        section                 1.6    inches                                         Downstream diameter of the venturi                                            reaction section        3      inches                                         Angle of the converging portion (upstream                                     frustoconus) to the axis of the reactor                                                               15°                                            Angle of the diverging portion (downstream                                    frustoconus) to the axis of the reactor                                                               8°                                             ______________________________________                                    

In this reactor two runs were carried out. In one run no combustiongases were radially fed into the reactor, however, jacket airsurrounding the oil feed line was introduced to protect the oil feedline. In the next run the jacket air could be avoided since in radiallyoutward direction combustion gases were blown into the reactorpreventing the detrimental effect of the boundary layer flow on the fedoil line. The quantities of oil and gas fed are shown in the followingTable 8.

                  TABLE 8                                                         ______________________________________                                                     Control Without                                                               Radial      With Radial                                                       Counterflow Counterflow                                          ______________________________________                                        Oil fed axially through the                                                   upstream end wall (lb/hr)                                                                    84.3          96.4                                             Tangential air (scfh)                                                                        9,000         9,000                                            Tangential gas (C.sub.3 H.sub.8 scfh)                                                        255.6         255.6                                            Jacket air (scfh)                                                                            262           --                                               Radial air (scfh)                                                                            --            1,000                                            Radial gas (C.sub.3 H.sub.8 scfh)                                                            --            42                                               ______________________________________                                    

The properties of the carbon black made as well as the pressure dropmeasured are shown in the following Table 9.

                  TABLE 9                                                         ______________________________________                                                         Control                                                                       Without                                                                       Radial   With Radial                                                          Counterflow                                                                            Counterflow                                         ______________________________________                                        Surface area of the carbon black                                              measured by nitrogen absorption                                               (N.sub.2 SA) M.sup.2 /g                                                                          140        135                                             Surface area of the carbon black                                              measured by cetyltrimethyl-                                                   ammonium bromide absorption                                                   (CTAB) m.sup.2 /g  135        128                                             Structure measured after compres-                                             sion four times 24,000 psi by di-                                             butylphthalate absorption cc/100 g                                                               91         99                                              Yield, lb/gal. of oil charged                                                                    3.94       4.59                                            Yield, lb/gal. of oil charged                                                 adjusted to 140 m.sup.2 /g N.sub.2 SA                                                            3.94       4.45                                            Yield % of total carbon, by wt.                                                                  36.7       42.9                                            Yield, % of total carbon, adjusted                                            to 140 m.sup.2 /g N.sub.2 SA, by wt.                                                             36.7       41                                              Pressure drop = p.sub.1 - p.sub.2 (inch Hg)                                                      5          3                                               ______________________________________                                    

The results of these runs show the following. By the boundary layerinterruption of this invention the yield based on the same surface areaof the carbon black is increased by about 12 percent. The pressure dropis improved by more than 40 percent (considering the pressure drop inthis example it is to be kept in mind that 9,262 scfh of air areintroduced into the reactor in the control run whereas 10,000 scfh ofair are introduced in the run in accordance with this invention); andthe structure of the carbon black is increased by eight points using theradial boundary counterflow as compared to a carbon black without such acounterflow.

The following calculated example is given to illustrate the operation ofa large particle size reactor shown in FIGS. 3 and 4.

EXAMPLE V

A reactor as described is employed having dimensions shown in thefollowing:

                  TABLE 10                                                        ______________________________________                                        Internal diameter of the reactor                                                                      40     inches                                         Axial distance of the center of the                                           tangential orifices from the                                                  upstream end wall       4.5    inches                                         Diameter of the tangential orifices                                                                   5.5    inches                                         Radial distance of the radial orifices                                        from the longitudinal axis                                                                            5      inches                                         Diameter of the radial orifices                                                                       0.75   inch                                           Axial distance of the secondary air inlets                                    from upstream end wall  12     feet                                           ______________________________________                                    

Into this reactor Gulf oil having a Bureau of Mines Correlation Index of120 and an average boiling point of about 800° F. is axially introduced.Hot combustion products from combustion of a mixture of air and naturalgas is radially and tangentially introduced into the reactor. Jacket airwas blown through the tube 6 surrounding the oil inlet line. Secondaryair 21 is fed into the reactor in radially inward direction. It isexpected that the carbon black produced will have an improved and moreuniform particle size distribution as compared to the carbon blackproduced by the same process and reactor, however, without radialcounterflow. The quantities of oil and gases fed into the reactor inaccordance with this example are shown in the following:

                  TABLE 11                                                        ______________________________________                                        Oil axially through upstream end wall                                                                100    gph                                             Tangential air         17     MSCFH                                           Tangential natural gas 0.9    MSCFH                                           Radial air             3      MSCFH                                           Radial natural gas     0.4    MSCFH                                           Secondary air          10     MSCFH                                           Jacket air             5      MSCFH                                           ______________________________________                                    

In addition to the improved qualities of the carbon black, the upwardlydirected back flow of gases and the overheating of the top of thereactor caused thereby can be avoided by the radial counterflow. Theback flow can also diffuse partly to the vertical wall because of thelarge scale turbulences existing in the reactor without the radiallyoutwardly directed counterflow.

In the following calculated example the invention is illustrated inconnection with a reactor shown in FIGS. 5 and 6.

EXAMPLE VI

The internal dimensions of the reactor employed in this example areshown in the following:

                  TABLE 12                                                        ______________________________________                                        Axial length of precombustion chamber                                                                  12     inches                                        Diameter of precombustion chamber                                                                      37     inches                                        Diameter of the tangential orifices                                                                    12     inches                                        Radial distance of the radial orifices                                        from the longitudinal axis                                                                             3.5    inches                                        Diameter of the radial orifices                                                                        1.5    inches                                        Upstream diameter of the venturi reaction                                     section                  15     inches                                        Throat diameter of the venturi reaction                                       section                  7      inches                                        Downstream diameter of the venturi reaction                                   section                  15     inches                                        Angle of the converging frustoconical venturi                                 wall (upstream portion) to the axis                                                                    15°                                           Angle of the diverging frustoconical venturi                                  wall (downstream portion)                                                                              8°                                            Distance of the hydrocarbon feed orifices                                     23 from the throat in downstream direction                                                             1.5    inches                                        (Obtuse) Angle of the hydrocarbon feed tubes                                  to the longitudinal axis 118°                                          ______________________________________                                    

For the operation of this reactor Gulf oil having a Bureau of MinesCorrelation Index of 120 and having an average boiling point of about800° F. is axially fed through the upstream end into the reactor. Thesame oil is fed downstream of the throat of the venturi into thereactor. Through the tangential ports hot combustion products fromburning natural gas and air are introduced, and through the eight radialtube outlets hot combustion products burning natural gas and air areintroduced at an approximate radial jet speed at the orifice of 250 feetper second. The quantities of oil and gases introduced into this reactorare shown in the following:

                  TABLE 13                                                        ______________________________________                                        Oil axially through upstream end wall                                                                60     gph                                             Oil downstream of the venturi throat                                                                 140    gph                                             Tangential air         130    MSCFH                                           Tangential natural gas 8.5    MSCFH                                           Radial air             20     MSCFH                                           Radial natural gas     1.5    MSCFH                                           Jacket air             4      MSCFH                                           ______________________________________                                    

The pressure drop between a point within the tangential tunnel 81 closeto the outlet 8 to about 15 reactor diameters downstream of the upstreamend wall of the reactor without radial counterflow is 4.5 psi. Theradial counterflow will reduce this pressure drop by 40 percent down toabout 2.7 psi. This pressure drop is only about 0.5 psi above thepressure drop of the comparable conventional reactor with a cylindricalreaction section having 12 inch diameter.

The following is a calculated example of the operation of the reactorshown in FIGS. 7 and 8.

EXAMPLE VII

The reactor employed in this example had dimensions as shown in thefollowing:

                  TABLE 14                                                        ______________________________________                                        Axial length of the precombustion chamber                                                              12    inches                                         Diameter of the precombustion chamber                                                                  37    inches                                         Diameter of the tangential conduits and                                       orifices                 12    inches                                         Radial distance of the radial orifices from                                   the longitudinal axis    4     inches                                         Axial distance of the centers of the radial                                   orifices from the upstream confining wall                                                              3     inches                                         Diameter of the radial orifices                                                                        1     inch                                           ______________________________________                                    

Into this reactor Gulf Oil having a Bureau of Mines Correlation Index of120 and an average boiling point of about 800° F. is axially introduced.Natural gas and air are fed tangentially and radially inwardly into thereactor. Jacket air is fed axially surrounding the oil feed line inorder to protect said line. The linear speed of the radially inwardlydirected stream of combustion gases is about 700 feet per second. Thequantities of gases and oil which are fed are shown in the following:

                  TABLE 15                                                        ______________________________________                                        Oil axially fed (gph) 260                                                     Tangential air (MSCFH)                                                                              170                                                     Tangential natural gas (MSCFH)                                                                      15.5                                                    Radial air (MSCFH)    20                                                      Radial natural gas (MSCFH)                                                                          2.7                                                     Jacket air (MSCFH)    4                                                       ______________________________________                                    

The introduction of stoichiometrically composed hot combustion gasesinto the hydrocarbon feed stream will result in a very rapiddecomposition of the hydrocarbon and following this rapid firstdecomposition in a formation of the hydrocarbon with high structure.

Reasonable variations and modifications which will be apparent to thoseskilled in the art can be made in this invention without departing fromthe spirit or scope thereof.

I claim:
 1. In a process for the production of carbon black by thepyrolytical decomposition of hydrocarbons comprising the steps(a)introducing hydrocarbons along the axis of a tubularly shapedlongitudinal reactor having an upstream confining wall, (b) introducinghot combustion gases of nonstoichiometric composition tangentially intosaid reactor at a location close to said upstream confining wall to forma vortex of hot combustion gases spinning around the axial hydrocarbonstream, (c) withdrawing carbon black containing smoke from the downwardend of said reactor, the improvement comprising (d) introducing hotcombustion gases of nonstoichiometric composition opposite to thenonstoichiometric composition of the tangentially introduced hotcombustion gases radially inwardly toward its longitudinal axis into thereactor from orifices located radially at a distance from the axiallyintroduced hydrocarbon stream and located axially at a distance fromsaid upstream confining wall and located within said vortex, thenonstoichiometric compositions of said tangentially introduced hotcombustion gases as well as of said radially inwardly introduced hotcombustion gases being such that said radially inwardly introduced hotcombustion gases mixed with a portion of the tangentially introduced hotcombustion gases form a stoichiometric hot combustion gas mixture, and(e) contacting said stoichiometric hot combustion gas mixture with saidaxially introduced hydrocarbon stream to effect pyrolyticaldecomposition thereof.
 2. A process in accordance with claim 1 whereinsaid reactor comprises a wide precombustion chamber defined by saidupstream confining wall, a cylindrical wall and a downstream confiningwall arranged essentially orthogonally to said longitudinal axis,whereinsaid reactor further comprises in axial alignment and open communicationwith said precombustion chamber a narrower reaction section, wherein thehydrocarbons are introduced axially through said upstream confiningwall, wherein the combustion gases in step (b) are tangentiallyintroduced through said cylindrical wall and wherein the combustiongases in step (d) are introduced through a plurality of individual axialconduits extending axially through the upstream confining wall andending turned 90 degrees within the reactor from the axial directiontoward the longitudinal axis and being arranged symmetrically around thelongitudinal axis, the ends of said conduits facing radially inwardlytoward the axis.
 3. A process in accordance with claim 1 wherein theradially inwardly introduced hot combustion gas stream is introduced insuch a manner as to flow into the axial hydrocarbon stream, but notradially out of this stream.
 4. A carbon black reactor comprising:(a) ahousing with tubular-shaped interior from heat resistant material havingan upstream confining wall arranged essentially orthogonally to thelongitudinal axis of the reactor, (b) first conduit means for axialintroduction of hydrocarbon feed into said housing, said first conduitmeans being arranged extending axially through said upstream confiningwall, (c) a cylindrical portion of said housing attached to saidupstream confining wall, (d) second conduit means for tangentialintroduction of combustion gases into said housing, said second conduitmeans being arranged extending tangentially through said cylindricalportion of the housing close to said confining wall, (e) third conduitmeans for radially inward introduction of a gas into said housing, saidthird conduit means comprising a plurality of conduits extending intothe interior of the reactor and ending in openings facing the stream ofaxially introduced hydrocarbon feed, said conduits extending axiallythrough said confining wall and end turned 90° from the axial directiontoward the radial direction, (f) means to withdraw the carbon blacksmoke from the downstream end of the reactor.
 5. A reactor in accordancewith claim 4 which comprises a precombustion section defined by saidupstream confining wall, said cylindrical wall and a downstreamconfining wall arranged essentially orthogonally to the longitudinalaxis of the reactor,and in axial alignment and open communication withsaid precombustion section a reaction section of smaller diameter thanthe cylindrical wall of the precombustion section.
 6. A reactor inaccordance with claim 5 wherein the reaction section is confined by awall having a cylindrically shaped interior.
 7. A reactor in accordancewith claim 5 wherein the reaction section is defined by a wall having aventuri-shaped interior.
 8. A reactor in accordance with claim 5 Whichcomprises a totally cylindrically shaped combined precombustion andreaction section connected to said upstream confining wall.
 9. A reactorin accordance with claim 4 wherein:(a) said housing comprises anupstream confining wall arranged essentially orthogonally to thelongitudinal axis, (b) said first conduit means are arranged axiallyextending through said upstream confining wall, (c) said upstreamconfining wall is attached to a cylindrical portion of the housing, (d)said second conduit means are arranged extending tangentially throughsaid cylindrical portion of the housing close to said upstream confiningwall, (e) said third conduit means comprises a plurality of individualtubes extending axially through said confining wall and being bent by 90degrees toward the axis of the reactor to form orifices facing radiallyinwardly and being located at a radial distance from the hydrocarbonfeed stream and at an axial distance from the upstream confining wall,(f) said second conduit means are connected to a first source of fueland oxygen in nonstoichiometric composition, and (g) said third conduitmeans are connected to a second source of fuel and oxygen innonstoichiometric composition opposite to the first source.